Oil Pressure

[jonlabree]

What is normal oil pressure for a 3800 engine.

At Idle and at speed?

[Barney Eaton]

The 1988-'89 owners will need to answer this question as the '90-'91 oil pressure gage does not have numbers........on the late models, the middle of the gage is "normal"

I have often wondered if the late car has some sort of "buffer" as the cars I have owned the gage does not move.

[2seater]

I have the original short-block engine back in the car now with a permanent oil pressure gauge in the feed line to the turbocharger. This engine has approx. 110k miles on it and it shows 42-45psi oil pressure at hot idle and 50-55 hot at 1800rpm. This is full synthetic 0w-30 motor oil. 

[jonlabree]

The reason I ask is that I have a "souped up" rebuilt oil pump and I pin the gauge on the dash, but the "real" gauge

reads 65 -70 bs cold and around 45-48 hot.

[2seater]

4 minutes ago, 63viking said:

The reason I ask is that I have a "souped up" rebuilt oil pump and I pin the gauge on the dash, but the "real" gauge

reads 65 -70 bs cold and around 45-48 hot.

That sounds similar to mine except the dash gauge goes to about 3/4 cold when above idle. Is it possible the oil sender is incorrect? I seem to remember a different calibration from year to year but it may be a false memory.

[jonlabree]

I have tried several sending units and I still get the same readings.

Since the last time I had the engine apart the pressure has been up.

But that's the way I like it. I also have a six quart oil pan.

[padgett]

OK first the relief valve is set for about 50 psi on the "C" engine and 65 psi on the "L" (91). Cold oil will exceed the relief capability.

Second the Georotor oil pump is very stable.

Third sending units are notorious for failing (I keep a spare handy).

Finally can read the sensed oil pressure directly at BD71.

[2seater]

8 minutes ago, padgett said:

OK first the relief valve is set for about 50 psi on the "C" engine and 65 psi on the "L" (91). Cold oil will exceed the relief capability.

Second the Georotor oil pump is very stable.

Third sending units are notorious for failing (I keep a spare handy).

Finally can read the sensed oil pressure directly at BD71.

Agree with all of that. I shim my relief spring a bit as I use an aftermarket oil cooler.

[jonlabree]

I also shim the relief spring to increase the pressure.  With the pressure of the supercharger I think it is wise to do so.

[Ronnie]

When building Chevy racing engines high oil pressure isn't desirable. It takes horsepower to turn an oil pump under high pressure. I have a friend with an automotive machine shops that builds racing engines for several drag racers. He is happy with 20 psi idling and 40-50 psi at high RPM when the engine is hot. He uses high performance oil pumps like Melling that are "high volume" oil pumps. They are able to keep lots of oil flowing through race engines that are built with more bearing clearance. The larger amount of oil flowing through the engine helps cool the bearings as well as the bottom side of the pistons.

[padgett]

+1 on that. Old time rule was 10 psi/1000 rpm. Any more I just run HiMilage Mobil 1 10w-30. Do remember back in the day Chevvy racing saying no more than 70 psi or it was liable to erode the bearings. Chevvy do have gear oil pumps so psi is more linear per rpm than a 3800.